The present invention relates to a side-push type push-on switch for use in operating sections of various kinds of electronic apparatus. A method for mounting the switch is also included.
There is an increasing need for inexpensive push-on switches that can be operated with a sidewise push force, or an operating force exerted in a direction parallel to the surface plane of a printed circuit board. Also, in view of the prevailing trends for downsized equipment and the preference for slim-shaped designs in the market of electronic apparatus, switches for such apparatus are requested to be small enough to satisfy various designing requirements.
A side-push type push-on switch known to meet the above-described general requirements is disclosed in Japanese Utility Model Laid-open Publication No. 51126.
FIG. 15 shows a cross-sectional side view of a conventional push-on switch, and FIG. 16 is an exploded perspective view. As shown in FIG. 16, a resin case 1 that opens upward is provided in its inner recess with a pair of outer fixed contact points 2 and a central fixed contact point 3 formed integrally by insert molding. The respective fixed contact points 2 and 3 are electrically coupled with terminals 4 provided on an outside wall surface of the resin case 1.
A rectangular movable contact 5 made of an elastic thin metal sheet is formed of a frame 5A and a bridging arch 5B disposed in the middle of the frame 5A. The movable contact 5 is placed so that the frame 5A makes contact with the outer fixed contact points 2.
The bridging arch 5B of movable contact 5 is held above the central fixed contact point 3 with a certain specific clearance.
Placed further above are a flexible anti-dust sheet 6 made of an insulating resin and an operating member 7.
The operating member 7 consists of an operating section 8 protruding toward the front from an opening 1A of side wall of case 1, and a flat plate section 9 formed integrally behind the operating section 8. The flat plate section 9 is provided in the middle part with a C-shaped vacancy 10 (xe2x80x9cC-shapedxe2x80x9d includes a square shape without one side), with its opening facing the front; the remaining central portion has a thinned area 12 at a stem region so that the central portion functions as a pushing section 11, which pushes the contacts.
The operating member 7 is placed, at the flat plate section 9, on a step existing around the recess of case 1 so that the pushing section 11 is located above the bridging arch 5B of movable contact 5.
A press board 13 is attached on the case 1 covering the flat plate section 9 of operating member 7, with claws 13A hooked to recesses 1B provided on the outer wall.
Thus the flat plate section 9 is supported between the step existing around the recess of case 1 and the bottom surface of the press board 13, and the operating member 7 can slide to-and-fro.
In the press board 13, an xe2x80x9cLxe2x80x9d-shaped bracket 15 is formed downward between a pair of slits 14. The steep-angled front face of bracket 15 contacts with the tip end 11A of the pushing section 11 of the operating member 7.
The above-configured conventional push-on switch is, in a normal mounting method, put on a printed circuit board and soldered, at its external connection terminals 4, with a circuit pattern (not shown) formed on the printed circuit board (not shown) of an apparatus, with the operating section 8 protruded from the front edge.
As to the operating mechanism of the conventional push-on switch, when the operating section 8 of operating member 7 protruding from the front edge of the printed circuit board is pressed towards a direction as indicated by an arrow in FIG. 15, the flat plate section 9, which is an integral part of the operating section 8, moves together along a space formed by parallel surfaces of the case 1 and the press board 13. The pushing section 11 moves in the same direction as well.
Since the pushing section 11 is in contact, at the tip end 11A, with the steep-angled front face of the bracket 15 of press board 13, the whole pushing section 11 bends downward with the thinned area 12 formed at the stem as the fulcrum. The bottom surface of tip end 11A of pushing section 11 pushes the bridging arch 5B of movable contact 5 down via the anti-dust sheet 6, and then the bridging arch 5B is reversed to mechanically contact, at its bottom surface, with the central fixed contact point 3. The outer fixed contact points 2 and the central fixed contact point 3 are made to have an electrical contact via the movable contact 5; or, the switch is brought to ON state.
When the pressure on the operating section 8 is withdrawn, the pushing section 11 is pushed back to its upper position by an elastic restorative force of the bridging arch 5B of movable contact 5, and slides along the bracket 15 to return to the original position; thus, the switch returns to the OFF state as shown in FIG. 15.
In the above-configured conventional push-on switch, the pushing section 11 needs to be provided in the operating member 7; therefore, a C-shaped vacancy 10 has to be formed in the flat plate section 9 and a thinned area 12 must be created at the stem. In order to meet the stricter requirements for downsizing, it is desired for the length of the pushing section 11 of operating member 7 to be shorter, the thickness of the thinned area 12 is to be reduced a step further, and also the size of the movable contact 5 is to be still smaller. This means that it is necessary to make more precise machining for the dies and molds, and to provide more severe controls over, for example, the flow characteristics of resin materials, the conditions for operating the molding machines, as well as the maintenance of precision dies and molds and other items. This inevitably results in a higher cost.
Conventionally, the mounted switches are fixed only by soldering the terminals 4 on a printed circuit board. Therefore, the conventional switches are vulnerable to operating forces exerted in parallel with the printed circuit board. Enhancement of the mounting strength has been an outstanding item that needs improvement with the conventional push-on switches.
The present invention addresses the above tasks for improvement, and aims to provide a compact side-push type push-on switch. Die and mold machining and preparation of constituent parts for the push-on switch of the present invention are easier and lower in total cost. In the push-on switches of the present invention, operating forces exerted onto the switch are encountered by the end-face at the edge of a printed circuit board.
A switch of the present invention comprises:
an insulating resin case containing a main body of a switch mechanism formed in a front-open cavity, where a central fixed contact point and an outer fixed contact point are fixed on the inner surface of a recess;
a domed movable contact housed in the recess, the movable contact constituting the switching contact element coupled with the fixed contact points; and
an operating body supported by a cover so that it can move to-and-fro for pushing at the rear end the domed movable contact.
The resin case is provided with an overhang which stretches (extends) horizontally from the case in the upper part of a region corresponding to the main body of the switch mechanism for a distance greater than the size of main body region. The overhang is provided with terminals, electrically coupled with the central fixed contact point and the outer fixed contact point, respectively.
Thus, a complex mechanism conventionally needed for converting a sidewise operating force into a switching action is replaced by a simple structure. Namely, in a side-push type push-on switch of the present invention, the domed movable contact is pushed directly by the rear end of an operating body which can move to-and-fro in the direction of the operating force.
The constituent components of the above-configured push-on switch are of simple construction, so they can be prepared through simple and easy procedures of mold machining and/or other manufacturing processes at low cost. In addition, the push-on switch operates with a superior functional feeling.
Furthermore, the push-on switch of the present invention is mounted on a printed circuit board with the back wall of the case, in the main body region, making contact with the end-face of a cut provided in a printed circuit board while a bottom of the overhang is immediately contact on to the upper surface of the printed circuit board, and the terminals provided in the overhang are connected with respective circuit patterns on the printed circuit board. Therefore, the operating force applied to the operating body is ultimately encountered by the end-face of the printed circuit board in an area behind the main body. Thus high connection reliability is ensured in the present push-on switches with respect to the printed circuit board.